CBSE Class 10 Science 2019 Delhi Set 3

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Question : 9
Total: 9
(a) Draw magnetic field lines produced around a current carrying straight conductor passing through a cardboard. Name, state and apply the rule to mark the direction of these field lines.
(b) How will the strength of the magnetic field change when the point where magnetic field is to be determined is moved away from the straight wire carrying constant current? Justify your answer.
Solution:  
(a) Right Hand Thumb rule is used to mark the direction of magnetic field lines produced around a straight current carrying conductor.
The Right Hand Thumb rule indicates the direction of magnetic field for a known direction of current. When the thumb is in downwards direction then the direction in which fingers are wrapped is clockwise. So magnetic field is clockwise.
(b) To determine the magnetic field, compass needle is used. On moving away from the compass needle from the straight wire, the deflection of the compass needle decreases showing the decrease in the strength of magnetic field. It happens because the strength of magnetic field produced by a straight wire at any point, is inversely proportional to the distance of wire from the point.
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